Adsorption apparatus comprising a heat recovery system

ABSTRACT

The invention relates to an adsorption machine, comprising
         at least a first and a second adsorber unit which are each connected to a forward motion (VL) and a return motion (RL), in order to supply heat from a heat transfer medium of the adsorber unit conducted through the forward motion (VL) to the adsorber unit or to remove said heat from the adsorber unit to the heat transfer medium;   each adsorber unit works alternately in a desorption phase as a desorber, wherein heat is removed from the heat transfer medium to the desorber and in an adsorption phase as an adsorber, wherein heat is removed from the adsorber to the heat transfer medium;   the adsorption machine comprises further at least two heat transfer medium circuits, namely a heating circuit with a heat source for heating up of the heat transfer medium, and a cooling circuit with a heat sink for cooling of the heat transfer medium.       

     The invention is characterized in that a control unit is provided which switches the forward motions (VL) and the return motions (RL) individually alternately to the heating circuit and the cooling circuit in such a way that the return motion with the highest temperature always feeds its heat transfer medium to the heating circuit.

The subject matter of the present invention is an adsorption machine, inparticular an adsorption cooling machine for refrigeration.

Thermally driven adsorption machines on the basis of solid adsorptionfor heating and cooling purposes have been known for some time. In theprocess conventional working substance pairs—sorption material andadsorbate—such as for example zeolite and water are used. Adsorptionmachines with such a working substance pair are for example describedwith DE 198 34 696, DE 199 61 629, DE 100 38 636, DE 101 59 652 or DE102 17 443.

Various technical demands are made on adsorption machines. Particularlyimportant are the demands for a high thermal ratio, a high power densityand an easy adjustability of the heat loss. The thermal ratio of theeffective heat to the driving heat—here and in the following namedCoefficient of Performance (COP)—depends essentially on the shares ofthe sorptive and of the sensitive heat transformation during anoperating cycle. By sorptive transformation one understands the releaseof the sorption heat arising in the case of the adsorption of theworking gas or the absorption of the sorption heat required fordesorption, whereas the sensitive heat transformation describes theenergy turnover which occurs in the case of the heating up or coolingdown of the entire system.

In order to achieve particularly high thermal ratios more and moresophisticated systems were developed, wherein in particular through thearrangement of a multitude of adsorber units, which are permeatedsuccessively by the heat transfer medium and switched in a multitude ofcycles, the highest possible heat recovery is strived for. By heatrecovery one understands any recovery of heat—sorptive as well assensitive—from the adsorption phase, wherein the recovered heat can beused for the desorption phase, in order hence to reduce the energyexpenditure of external heat sources for the desorption.

Adsorption machines with two adsorber units are conventionally used forrefrigeration. In these refrigerating machines the adsorber units workalternately as adsorbers or desorbers. The conventional control systemsin the process work between the adsorption phases with heat recoveryphases which partially conduct the heat energy of the adsorber unit thatis still hot to the adsorber unit that is still cold. Through these heatrecovery phases the energy present in the system is reused to a certainextent, so that less energy must be supplied from the outside. Theefficiency of this heat recovery is thus critical for the efficiency ofthe entire adsorption machine.

Conventional control system concepts conduct the heat transfer mediumduring the heat recovery phase in parallel or serial fashion throughboth adsorbers. For this purpose additional components are required, forexample reversing valves or pumps in the heat transfer medium circuitsystem. Moreover this heat transfer medium circuit is operated uncoupledfrom the other circuits. This leads to the pumps mostly connectedexternally to the adsorption machine not being able to send anyvolumetric flow through the system during the time of the heat recoveryand must either be switched off or conducted past the system in abypass. The disadvantages of these systems are the considerabletechnical expenditure, the susceptibility to failure and the highmanufacturing and maintenance costs.

The invention is based on the object of specifying an adsorption machineand a method for heat recovery in an adsorption machine which areimproved with regard to the named disadvantages. In particular thenumber of components should be reduced in comparison with the knownadsorption machines without worsening the heat recovery, but ratherpossibly improving said heat recovery. In particular the heat recoveryshould be able to be performed without interruption of externallyapplied volumetric flows.

The object according to the invention is solved by an adsorption machinewith the features of Claim 1 and a method with the features of Claim 12.The dependent claims describe advantageous and particularly expedientembodiments of the invention.

The adsorption machine according to the invention comprises in otherwords at least a first and a second adsorber unit, a heat transfermedium and at least two heat transfer medium circuits with a temperaturedifference ΔT_(X), of which one heat transfer medium circuit is aheating circuit and the other heat transfer medium circuit is a coolingcircuit. Each adsorber unit works in a first desorption phase as adesorber and works in a second adsorption phase as an adsorber, whereinthe heat transfer medium exhibits a lower temperature in a return motionfrom a desorber than in a forward motion to the desorber, and the heattransfer medium exhibits a higher temperature in a return motion from anadsorber than in a forward motion to the adsorber.

Consequently the heat transfer medium is cooled from a forward motion inan adsorber unit working as a desorber, because heat is transferred fromthe heat transfer medium to the adsorber unit, and the heat transfermedium is heated up from a forward motion in an adsorber unit working asan adsorber, because heat is transferred from the heat transfer mediumto the adsorber unit.

The heating circuit basically serves the purpose of transferring heatfrom a heat source which is connected to the heating circuit to the heattransfer medium so that said heat transfer medium can heat up thedesorber. The cooling circuit basically serves the purpose of removingheat from the heat transfer medium by means of a heat sink so that saidheat transfer medium can cool the adsorber.

The heating circuit can also be described as a high temperature circle(HT circle) and the cooling circuit can be described as a meantemperature circuit (MT circle). Accordingly by HT source the heatsource of the heating circuit is meant and by MT sink the heat sink ofthe cooling circuit is meant, see FIG. 1.

The temperature difference between the high temperature circuit and themean temperature circuit is presently termed as ΔT_(X), wherein thetemperature T_(H) corresponds to the upper limit of the temperaturedifference ΔT_(X) of the two heat transfer medium circuits. Thetemperature T_(H) is that temperature to which the heat transfer mediumshould be set in the high temperature circuit.

The temperature T_(M) corresponds to the lower limit of the temperaturedifference ΔT_(X) of the two heat transfer medium circuits and thattemperature to which the heat transfer medium should be set in the meantemperature circuit.

Through the embodiment according to the invention an adsorption machinecan be created whose heat recovery is at least as great as in the caseof conventional adsorption machines and which in the process manageswithout the integration of additional components in the machine.

In particular the heat recovery of the adsorption machine according tothe invention can take place as a subprocess integrated in the totalprocess, wherein no volumetric flow interruption occurs. The heatrecovery can take place solely with valves and in particular pumps,which are required for the sorption phases anyway.

In particular in an adsorption machine in accordance with the presentinvention provision is made that the temperature difference ΔT_(X) is atleast 10° C. in particular at least 20° C. and especially preferably atleast 25° C. In the process in particular provision can be made that theheat transfer medium in the high temperature circuit exhibits atemperature T_(H) of at least 70° C. and a maximum of 90° C., and inparticular from 75 to 85° C. In principle the adsorption machineaccording to the invention or the method according to the invention ishowever suitable for any temperature differences and temperature level.

In an alternative embodiment of the invention an adsorption machineaccording to the invention can exhibit three heat transfer mediumcircuits, wherein the high temperature circuit exhibits a temperaturedifference ΔT_(X) to a second mean temperature circuit and exhibits atemperature ΔT_(Y) to a third lower temperature circuit, and wherein thetemperature difference ΔT_(Y) is greater than the temperature differenceΔT_(X).

With an adsorption machine according to the invention advantageouslyeach adsorber unit is not firmly connected to a heat transfer mediumcircuit or assigned to it as usual, but rather is assigned to a heattransfer medium circuit dependent on its temperature in the returnmotion. This is in particular achieved as a result of the valves notboth being positioned in the same direction in the forward and returnmotion of a component in a control phase, but rather having the positionmade dependent on the adjacent temperature level. In an adsorptionmachine according to the invention the valves can be positioned in theforward motion of both adsorber units at the beginning of the heatrecovery phase in such a way that the “new” desorber receives the heattransfer medium from the high temperature circuit and consequently isheated up. The return motion of this “new” desorber, which is stillcold, however continues to be conducted to the mean temperature circuituntil the temperature level increases significantly, in particular by apreset extent or to a temperature equal to or above the return motion ofthe “old” desorber, which is the “new” adsorber. Similar to this theforward motion of the “new” adsorber is connected to the meantemperature circuit, so that this “new” adsorber is cooled. The returnmotion of the “new” adsorber, which is still hot, however continues tobe connected to the high temperature circuit until the temperature leveldecreases significantly, in particular by a preset extent or to atemperature equal to or below the return motion of the “old” adsorber,which is the “new” desorber.

FIG. 1 shows a hydraulic diagram of an exemplifying embodiment of anadsorption machine according to the invention.

As one recognized in FIG. 1, the valves of the forward motion group ( .. . _VL_. . . ) are differently connected during the heat recovery thanthose of the return motion group ( . . . _RL_. . . ). One advantage ofthis adsorption machine consists in the fact that a heat recovery cantake place without interruption of the external volumetric flows.

With this during the heat recovery, the heat transfer medium isconducted to the high temperature circuit at all times with the highestavailable temperature in the return motion of the system. As a result ofthis, on the one hand the energy which must be provided from the outsideto the system is minimized and on the other hand through the embodimentof the adsorption machine it is also guaranteed that at all times theheat transfer medium will be conducted to the cooling circuit with thelowest temperature, so that the least possible energy must be recooled.In particular, the energy requirements are reduced when in accordancewith an embodiment of the invention pumps, as they are described in theintroductory part of the description with regard to the known controlconcepts, are conserved.

In particular an adsorption machine according to the invention comprisestwo adsorber units. These adsorption machines can in particular producecold in a two-stage, cyclical process. In order to generate a continuouscold flow at least two adsorber units are counter connected, so that oneadsorber unit is being dried while the other one produces cold.Fundamentally this process runs all the more effectively the more thesorption material has been dried previously—which in turn best succeedswith higher driving temperatures.

Accordingly an adsorption refrigerating machine is also the subjectmatter of the present invention. This adsorption refrigerating machinecomprises at least two adsorber units, one heat transfer medium, atleast two heat transfer medium circuits with a temperature differenceΔT_(X) and one control unit, wherein each adsorber unit works in a firstdesorption phase as a desorber and in a second adsorption phase works asan adsorber, and wherein the heat transfer medium in a return motion ofthe desorber exhibits a lower temperature than in the forward motion tothe desorber and wherein the heat transfer medium in a return motion ofthe adsorber exhibits a higher temperature than in a forward motion tothe adsorber, and wherein the heat transfer medium with the highesttemperature in the return motion of the first or any further adsorberunit is connected to the high temperature circuit.

Along with the adsorption machine itself a method for heat recovery inan adsorption machine in accordance with Claim 12 is also the subjectmatter of the present invention. In especially preferred manner in theprocess the temperatures of the return motions are compared with eachother and the return motion with the highest temperature is assigned tothe high temperature circuit.

The operating cycle of an adsorption machine according to the inventioncan flow as follows. First minerals with a large inner surface, inparticular zeolite or silica gels, are dried by heat supply during adesorption phase. When the material has been sufficiently dried the heatsupply is stopped and a valve to a water container is opened. Due to theenormous inner surface and the special crystal structure there is a verygreat suction of water vapor or the evaporating of water in the secondcontainer. As is the case with any evaporation process there is now agreat temperature decline in the water depending on the operating stateup to the formation of ice.

In order to produce a continuous cold flow two such systems are counterconnected so that one adsorber unit is drying while the other one isproducing cold. Alternately the present adsorption machine can comprisethree adsorber units or at least three adsorber units. In particularprovision is made in the process that one adsorption machine comprises amaximum of five adsorber units. In principle however the output of theadsorber machine can be continuously expanded by the simple addition offurther adsorber units.

With an adsorption machine in accordance with the present invention inparticular by a reduction of the necessary pumps the current consumptionand also the generation of noise can be significantly reduced. At thesame time the electrical efficiency is improved. For example theadsorption machine can exhibit pumps exclusively in the external heattransfer medium circuits, that is between the heat sources and/or heatsinks and the adsorber units, for example a single pump per eternalcircuit, as shown in FIG. 1. The adsorber units themselves can bedesigned free of pumps.

Waste heat or excess heat from existing systems can be used as a heatsource, for example engine-based cogeneration systems, solar plants orprocess waste heat.

1. Adsorptive machine, comprising at least a first and a second adsorberunit which are each connected to a forward motion (VL) and a returnmotion (RL), in order to supply heat from a heat transfer medium of theadsorber unit (1) conducted through the forward motion (VL) to theadsorber unit or to remove said heat from the adsorber unit to the heattransfer medium; each adsorber unit works alternately in a desorptionphase as a desorber, wherein heat is removed from the heat transfermedium to the desorber and in an adsorption phase as an adsorber,wherein heat is removed from the adsorber to the heat transfer medium;the adsorption machine comprises further at least two heat transfermedium circuits, namely a heating circuit with a heat source for heatingup of the heat transfer medium, and a cooling circuit with a heat sinkfor cooling of the heat transfer medium, wherein a control unit isprovided which switches the forward motions (VL) and the return motions(RL) individually alternately to the heating circuit and the coolingcircuit in such a way that the return motion with the highesttemperature always feeds its heat transfer medium to the heatingcircuit; characterized in that the control unit is designed in such away that in the transition of the first adsorber unit from thedesorption phase to the adsorption phase and in the transition of thesecond adsorber unit from the adsorption phase to the desorption phaseor vice versa first it connects the forward motion (VL) of the adsorberunit which is connected as the new desorber to the heating circuit sothat the new desorber is fed from the heating circuit and thus heatedup, and the return motion (RL) of this new desorber continues to beconnected to the cooling circuit until the temperature level of the heattransfer medium in the return motion (RL) is increased by a presetextent, or is warmer than the return motion (RL) of the other adsorberunit, and the return motion (VL) of the new adsorber is connected to thecooling circuit so that this new adsorber is cooled and the still warmreturn motion (RL) of the new adsorber continues to remain connected tothe heating circuit until the temperature of the heat transfer medium inthe return motion (RL) has decreased by a predetermined extent, or up toor below the temperature of the return motion (RL) of the other adsorberunit.
 2. The adsorption machine in accordance with claim 1 characterizedin that the control unit is designed in such a way that it alwaysswitches the return motion (RL) with the lowest temperature in such away that it feeds its heat transfer medium to the cooling circuit. 3.The adsorption machine according to claim 1, characterized in that atemperature difference ΔT_(X) between the heating circuit and thecooling circuit amounts to at least 10° C. or at least 20° C. or atleast 25° C.
 4. The adsorption machine according to claim 1,characterized in that the adsorption machine comprises three heattransfer medium circuits.
 5. The adsorption machine according to claim4, characterized in that the third heat transfer medium circuit is a lowtemperature circuit and exhibits a temperature difference ΔT_(Y) to theheating circuit, wherein the temperature difference ΔT_(Y) is greaterthan the temperature difference ΔT_(X).
 6. The adsorption machineaccording to claim 1, characterized in that the heat transfer mediumwith the lowest temperature is assigned to the low temperature circuit.7. The adsorption machine according to claim 1, characterized in thatthe adsorption machine comprises at least three adsorber units.
 8. Theadsorption machine according to claim 1, characterized in that water,water vapor or oil is used as the heat transfer medium.
 9. Theadsorption machine according to claim 1, characterized in that eachadsorber unit comprises zeolite as an adsorbing agent.
 10. Theadsorption machine according to claim 1, characterized in that theadsorption machine is a refrigerating machine.
 11. A method for heatrecovery in an adsorption machine comprising at least a first and asecond adsorber unit which are each connected to a forward motion (VL)and a return motion (RL), in order to supply heat from a heat transfermedium of the adsorber unit conducted through the forward motion (VL) tothe adsorber unit or to remove said heat from the adsorber unit to theheat transfer medium and further comprising at least two heat transfermedium circuits, namely a heating circuit with a heat source (3) forheating up of the heat transfer medium, and a cooling circuit with aheat sink (4) for cooling of the heat transfer medium, wherein eachadsorber unit works alternately in a desorption phase as a desorber,wherein heat is removed from the heat transfer medium to the desorberand in an adsorption phase as an adsorber, wherein heat is removed fromthe adsorber to the heat transfer medium; and the forward motions (VL)and the return motions (RL) are switched individually alternately to theheating circuit and the cooling circuit in such a way that the returnmotion with the highest temperature always feeds its heat transfermedium to the heating circuit; characterized in that in the transitionof the first adsorber unit from the desorption phase to the adsorptionphase and in the transition of the second adsorber unit from theadsorption phase to the desorption phase or vice versa first the forwardmotion (VL) of the adsorber unit which is connected as the new desorberis connected to the heating circuit so that the new desorber is fed fromthe heating circuit and thus heated up, and the return motion (RL) ofthis new desorber continues to be connected to the cooling circuit untilthe temperature level of the heat transfer medium in the return motion(RL) is increased by a preset extent, or is warmer than the returnmotion (RL) of the other adsorber unit, and the return motion (VL) ofthe new adsorber is connected to the cooling circuit so that this newadsorber is cooled and the still warm return motion (RL) of the newadsorber continues to remain connected to the heating circuit until thetemperature of the heat transfer medium in the return motion (RL) hasdecreased by a predetermined extent, or up to or below the temperatureof the return motion (RL) of the other adsorber unit.
 12. The method inaccordance with claim 11, characterized in that the return motion (RL)with the lowest temperature is always switched in such a way that itfeeds its heat transfer medium to the cooling circuit.
 13. The method inaccordance with claim 12, characterized in that the switching of theforward motions (VL) and of the return motions (RL) takes place by meansof a control unit which compares the temperatures of the return motions(RL) with each other.
 14. The method in accordance with claim 11,characterized in that the switching of the forward motions (VL) and ofthe return motions (RL) takes place by means of a control unit whichcompares the temperatures of the return motions (RL) with each other.15. The adsorption machine according to claim 2, characterized in that atemperature difference ΔT_(X) between the heating circuit and thecooling circuit amounts to at least 10° C. or at least 20° C. or atleast 25° C.
 16. The adsorption machine according to claim 2,characterized in that the adsorption machine comprises three heattransfer medium circuits.
 17. The adsorption machine according to claim3, characterized in that the adsorption machine comprises three heattransfer medium circuits.
 18. The adsorption machine according to claim2, characterized in that the heat transfer medium with the lowesttemperature is assigned to the low temperature circuit.
 19. Theadsorption machine according to claim 3, characterized in that the heattransfer medium with the lowest temperature is assigned to the lowtemperature circuit.
 20. The adsorption machine according to claim 4,characterized in that the heat transfer medium with the lowesttemperature is assigned to the low temperature circuit.